CHAPTER6 Silver nanoparticles as a catalyst for ...shodhganga.inflibnet.ac.in/bitstream/10603/35165/11/11_chapter6.pdf · Silver nanoparticles as a catalyst for degradation of hazardous

CHAPTER6

Silver nanoparticles as a catalyst for degradation of hazardous textile dye

• Abstract

6.1 Introduction

6.2 Experimental

6.2.1 Materials

6.2.2 Apparatus

6.2.3 Preparation of silver (Ag) nanoparticles

6.2.4 Batch degradation

6.2.5 Analysis of degraded products

6.3 Results and discussion

6.3.1 Characterisation

6.3.2 Kinetics of dye degradation

6.3.3 Identification of degraded product

6.3.4 Catalytic degradation

6.3.5 Degradation Pathway

6.4 Conclusion

• Figures and Tables

• References

Chapter 6 Silver nanoparticles

ABSTRACT

The degradation of five different categories of dyes in aqueous solutions was

investigated using silver nanoparticles as catalyst. Silver nanoparticles were prepared by

citrate reduction method and was characterized by Dynamic light scattering (DLS)

Transmission electron microscopy (TEM) and UV-Vis spectrophotometry. Red 5B

(R5B), Red 6BX (R6X), Acid orange 7 (A07), Orange 2R (02R) and Patent blue (PB)

were degraded by batch experiments with silver nanoparticles as nanocatalyst, which

showed complete degradation within 15 min of reaction time. The process was studied by

monitoring the simultaneous decrease in the height of absorbance peak of dye solution

and increase in the height or shifting of plasmon peak corresponding to silver

nanoparticles. The results show that silver nanoparticles are an efficient catalyst for

degradation of dyes and their efficiency depends on surfactant and its nature. The

analysis of the degraded products by chemical oxygen demand (COD), FT-IR

transmission, Mass spectrometry (MS) and Ion chromatography (IC) revealed that the

degradation mechanism proceeds through a reductive cleavage of the azo linkage

resulting in the formation of amines, sulphates, C02 and H20.

152


6.1 INTRODUCTION

Industrial development is pervasively connected with the disposal of a large

number of various toxic pollutants that are harmful to the environment and hazardous to

human health. It is difficult to degrade the pollutants by natural means. Synthetic textile

dyes and other industrial dyestuffs constitute the largest group of chemicals produced in

the world. Dye effluents discharged in rivers contaminate water and surrounding

environment. Aquatic animal and the biological processes in river get affected due to this

contamination. Thus the removal of dyes from industrial effluents is of great significance

in connection with environmental and human health safety. During the past decade, much

attention has been paid to investigate the degradation of dye pollutants with different

methods like photo catalytic degradation [1, 2], oxidative processes [3], biodegradations

[ 4, 5] etc. But these methods are time consuming and conditions are critical.

Photocatalytic degradation using titanium dioxide is also a technically viable clean-up

process for dyes [1, 2] but problems like low quantum yield and requirement ofUV light

hinder its widespread acceptance as a practical remediation technology. Therefore, a

rapid and easy method for degradation is desirable.

Synthesis of metal nanoparticles, their characterization and application to

different fields have become an important trend in the modem investigation.

Nanoparticles have unique chemical, electronic, magnetic and optical properties due to

their small size and high surface area [7-9]. Nanoparticles have found uses in many

applications like catalysis, drug delivery system, optoelectronics, magnetic devices etc

[10-12]. For example, due to specific optical properties, metal nanoparticles show

presence of strong absorbance band in the visible region, which is not found for bulk

153


metals. This absorbance band arises due to plasmon oscillation modes of conduction

electrons [ 13-15]. Due to this plasmon band optical properties of metal particles,

particularly of gold, silver and copper nanoparticles, have received considerable attention

[ 16-18]. Secondly metal nanoparticles, because of their larger surface area to volume

ratio and size dependent reactivity are found to be promising adsorbents and catalysts.

Silver nanoparticles have shown to be amazingly active and selective catalyst for various

important reactions [19-23].

Several physico-chemical and bio degradation techniques have been reported for

the degradation of dyes like catalytic degradation [ 1, 2], photo oxidative processes [3],

biodegradations [4, 5] etc. However, the time for the degradation by most of these

methods are higher. Biodegradation is an environmentally friendly and cost competitive

alternative but the conventional aerobic treatments have been proved ineffective while

highly toxic aromatic amines can be formed by reductive fission under anaerobic

conditions. Photo oxidative processes take much higher time with very low

concentration. Such degradant are not suitable for the large scale degradation treatment

purpose, especially as some ofthem can work only at limited pH value [4].

In the present investigation Ag nanoparticles were chosen for the first time to

study their catalytic reductive degradation capacities in presence of cationic and anionic

surfactants. Red 5B (R5B), Red 6BX (R6X), Patent blue (PB), Acid orange (AO) and

Orange 2R (02R) dyes, used extensively in textile industries, were chosen as model

compounds for batch degradation experiments. UV-Visible, FT-IR and GC-MS and IC

analysis of dye degradation directs the surface chemistry and drives the mechanistic

pathway of degradation. The research was targeted towards the study of ( 1) the efficiency

154


of the nanocatalst for the degradation of dye pollutants; (2) the interaction between the

dye and nanocatalyst in the aqueous systems, and (3) the mechanism of catalytic

enhancement of degradation of dye pollutants.

6.2 EXPERIMENTAL

6.2.1 Materials

AgN03 (crystal extra pure) was purchased from Merck. Sodium dodecyl sulphate

(SDS), cetyl trimethyl ammonium bromide (CTAB), sodium citrate and sodium

borohydride were obtained from Thomas Baker. Red 5B (R5B), Red 6BX (R6BX), Acid

orange (AO), Orange 2R (02R) and Patent blue (PB) dyes obtained from shree Uma dye

chemicals, Ahmedabad, India were used without further purification. All other chemicals

used were of analytical reagent grade. Deionized and doubly distilled water was used

throughout the study. The pH of the solution was adjusted with either dilute HCl or

NaOH. The structures ofthe dyes are given in Fig. 1.

6.2.2 Apparatus

The morphology and s1ze of the nanoparticles were estimated usmg the

transmission electron microscope (TEM) (PHILIPS TECNAI) operated at an accelerating

voltage of 120 kV and a magnification of 85000X. Samples were loaded on carbon

coated grids before being introduced into the vacuum chamber. The size distribution of

Ag nanoparticles was studied using Dynamic light scattering (DLS) (Nanotrac NPA

150/250). DLS analysis was done by dipping a probe of DLS in the dispersed Ag

nanoparticles. [Descreptin of DLS will be added from the reported paper later] UV-vis

absorption spectra were acquired on a Jasco V-570 UV-vis spectrometer. IR spectra

155


were measured with a Broker Tensor 27 FT-IR spectrometer. The degraded products

identification were done by Perkin-Elmer GC-MS and Dionex IC.

6.2.3 Preparation of silver (Ag) nanoparticles

The procedure for the preparation of Ag nanoparticles was essentially the same as

those developed by Turkevich [24] with difference only in the molar ratio of AgN03 to

sodium citrate. All glassware was thoroughly cleaned with freshly prepared 3: 1

HC1/HN03 (aqua regia) and rinsed thoroughly with deionized water prior to use. To

synthesize Ag nanoparticles in water, in a round bottom flask equipped with a condenser,

100 mL of 0.1 mM AgN03 was brought to a boil with vigorous stirring, and 10 mL of

17.0 mM sodium citrate (Aldrich) was rapidly added to the vortex of the solution. The

yellow solution was cooled to room temperature (25° C) by stirring for another 15 min.

The solution was then filtered through a 0.45 ~filter (Millipore, Nylon membrane).

6.2.4 Batch degradation

All the five dye stock solutions (1.0 x 104 M) were prepared in deionized water

and degradation experiments were performed in an open batch system at neutral pH and

room temperature. Sodium borohydride (1.0 x 10-3M) and SDS (1.0 x 10-2 M) surfactant

solutions were prepared by dissolving the requisite amount in deionized water. In a

typical experiment 100 ml (1.0 x 104 M) dye solution was mixed with 5.0 ml Ag

nanoparticles and 5.0 ml of surfactant SDS in 250 ml conical flask with stirring. To the

above mixture, 5.0 ml of sodium borohydride solution was added. The degradation of all

five dyes was completed within around 15 min.

156


6.2.5 Analysis of degraded products

The degraded products of the dye samples were analysed using UV-Vis, FT-IR, GC-MS,

IC and by measuring the chemical oxygen demand (COD) of the samples.

UV-Visible

The rate of degradation was monitored by measuring the absorbance of the

solution from 190 to 800 nm with a UV-Vis spectrophotometer.

FT-IR

The degraded product was analyzed using FT-IR from 4000 to 400 cm-1• TheFT

IR spectra of the dye samples before and after degradation were then compared.

GC-MS

The final degraded product was identified by in Perkin-Elmer GC-MS Clams 500.

Perkin-Elmer GC-MS Clams 500 equipped with DB 1 column, size 30 m X 0.32 mm,

0.25 11m (5° C/min) was used for the analysis.

Ion chromatography

Operating conditions of Dionex ICS 1000 were as follows: column, IonPac® AS-11

HC (4 x 250 mm); suppressor conductivity ASRS®ULTRA II 4-mm anion self- regenerating

suppressor (ASRS); eluent, 20 mM sodium hydroxide (Sigma-Aldrich); column temperature

25±2° C; flow rate 1.5 mllmin; injection volume, 25 11l; System backpressure 1920 psi; and

background conductivity: 22 !J.S.

Chemical oxygen demand

The chemical oxygen demand (COD) of the dye (50 mL of 1.0 x 104 M) was

measured directly, without removal of the silver nanoparticles and surfactant, after time

intervals using the titrimetric method [25]. 1 g of mercury sulphate was added to 50 mL

1.0 x 104 M dye solution, followed by 80 mL of a solution of silver sulphate in sulfuric

157

--------~-


acid. Then 10 mL of 0.00833 M potassium dichromate solution was added and refluxed

for 15 min. After cooling, added 1 mL of ferroin indicator and titrated with 0.025 M

ammonium iron sulfate solution. The end point is marked by the change of color from

blue to green. Calculated the COD using the equation given below.

COD= A-B x 0.2 x 20 mgL-1

Here, A is dye sample reading and B is blank titration reading.

6.3 RESULTS AND DISCUSSION

6.3.1 Characterisation

The TEM image of Ag nanoparticles with the size calibration is shown in Fig.2.

The particle size of Ag nanoparticles is in the range of 50-70 nm. Fig. 3 shows dynamic

light scattering histogram of Ag nanoparticles. The mean particle diameter obtained from

DLS graphs is 60.6 nm which supports the TEM results. The plasmon peak of Ag

nanoparticles was observed at 422 nm which is shown in Fig. 4.

6.3.2 Kinetics of dye degradation

The absorption spectra of an aqueous solution of all five dyes recorded is shown

in Fig. 5 (topmost). The molar absorptivity of dyes at the 1.0 x 104 M concentration

studied, which are measurably high (Table 1) even for dilute solutions and hence

photometric method was adopted for the investigation. Aqueous solutions of the dyes

were degraded within a period of 15 min, which can be inferred from the reappearance of

the color of the nanoparticles (Fig. 6). The present method of degradation is faster and

efficient than biodegradation using Comamonas sp. UVS bacteria, which take 125 h for

158


the degradation of Red 5B dye [5]. The absorption band of the dye disappeared

irreversibly (Fig. 5), indicating that the chromophoric structure of the dye was destroyed.

After the addition of the nanocatalyst, the dye solution was stirred for 15 min to

ensure that the equilibrium adsorption/desorption of the dye on the catalyst was attained.

The corresponding concentration of the dye (as measured by UV spectrophotometer and

the concentration evaluated using Beer-Lambert's law) was taken as the initial

concentration (1.0 x 104 M) of the dye for all the catalyzed reactions. Fig. 7 shows the

decrease in dye concentration with the time. From the results it can be concluded that

dyes degraded within 10-12 min which is faster than the previously reported methods [5].

Fig. 8 shows the variation of concentration profile of various dyes, at different

initial concentrations, in silver nanoparticles catalyzed system. The initial rates of the

reaction were determined by extrapolating the tangent (based on the linear fit of the first

four points) of the concentration profile back to initial conditions. The slopes (Table 2) of

logC vs time calculated were nearly constant, indicating the accuracy of the initial rate of

degradation in this study.

6.3.3 Identification of degraded products

The degraded products of the dye samples were identified using FT-IR,

GC-MS, IC and by measuring the chemical oxygen demand (COD) of the samples.

FT-IR

The variation of the IR spectra during the course of the nanocatalytic degradation

of dye is illustrated in Fig 10. The assignments for the principal bands in the IR spectra of

dyes (before degradation): around 1500-1400 cm-1 correspond to aromatic ring and C

aryl bond vibrations; 650 cm-1 are caused by vibrations in the S04-2

• During the

159

Chapter6 Silver nanoparticles

degradation process, bands of vibrations characteristic of the carbon-nitrogen bond, the

C-aryl bond, and nearly all of the aromatic skeletal vibrations decreased and disappeared.

The S04 .z absorption band was retained in the degraded product. Meanwhile, some new

IR absorption bands appeared in the region 900-650 cm·1 indicating a non-aromatic

structure of the band [25].

GC-MS

Gas chromatography-mass Spectrophotometry (GC-MS) was used to analyze the

degraded final products formed in the direct nanocatalytic degradation of the dyes. The

MS features confirm the major components of the all five dye degraded and fragmented.

Final products of the dyes are described in Fig. 11. Acid orange dye does not give any

final degraded product which depicts that complete mineralization of the dye.

Ion chromatography

The IC analysis of the degraded dye shows presence of S04•2 (Fig. 12) with two

overlapped chromatogram ofS04"2 peak at retention time 3.83 min. Since SDS is used as

a surfactant, the dye sample for degradation was also injected to IC before the addition of

nanoparticles and an increase in the peak height of So4•2 (gray peak) was observed due to

destruction of dyes.

Chemical oxygen demand

Fig. 9 shows the temporal changes of COD in the degradation of the dye, which

reflect the mineralization extent of the organics in the total dispersions (both in the bulk

and on the nanoparticles surface). The decrease in COD values of 1.0 x 104 M of dye

(100 mL) containing silver nanoparticles and surfactant also shows two different stages

before and after 5 min, 90.0 % of total COD was reduced before 10 min, indicating that

160


all the dyes investigated mainly underwent the destruction of the chromophore structure

within 5 min, and subsequent mineralization of the fragments occurred after 5 min.

6.3.4 Catalytic degradation

The degradation was very slow and insignificant in the absence of catalyst. The

characteristic absorption band of dye was not affected even after 20 min. However, when

Ag nanopaticles was added, the color of the dye started fading very fast which was

slowed down after a period of 5 min. This may be because of the tendency of Ag

nanoparticles to agglomerate, decreasing their surface area. It is also possible that in

presence ofNaBH4, the surface of Ag nanoparticles becomes vulnerable to oxidation and

their catalytic activity decreases [22]. The degradation was faster in presence of a

surfactant. The surfactant stabilizes the nanoparticles and keeps them dispersed, so that

large surface area of catalyst is available to the reactants. Moreover, the surfactant also

dissolves the oxide layer and makes the surface clear, and hence the degradation process

is not affected. We avoided the use of surfactant while synthesizing the nanoparticles

because presence of surfactant during the formation of nanoparticles influences the

particle size and shape [26-27].

To study the effect of pH, the degradation of all the dyes was carried out in a wide

range of pH from 2-10 [Fig. 12]. It was observed that the degradation is slower at pH<

7.0 in all the cases, while the complete degradation resulted within 10 min in basic

medium (pH 7- 10). The pH study ofR5B is shown in Fig. 12 as a representative case.

The influence of nature of surfactant on dye degradation process was studied and

it was found that the degradation was much faster when SDS was used as surfactant, with

CT AB the degradation becomes very slow (2 h) which may be due to the cationic nature

161


of the surfactant SDS is an anionic surfactant and when dye and surfactant molecules are

of similar charges, repulsive interaction will result and thus surfactant molecule will not

hinder the approach of dye molecule to the catalyst surface, which ultimately will result

in faster degradation.

6.3.5 Degradation Pathway

The process of degradation can be explained by electron transfer mechanism. The

reductant molecules and dye molecules probably get adsorbed on the large surface of

nanoparticles with out affecting their activity because of the presence of surfactant [Fig.

13]. The electrode potential of Ag/Ag+ is +0.80 V. When reducing agent NaBH4 is

adsorbed on the nanoparticles, its reductive potential decreases, as NaBH4 is a strong

nucleophile. On the other hand, when dye molecules get adsorbed on nanoparticles, their

reduction potential increase, as the molecules are electrophilic in nature and hence, when

both the species are adsorbed on nanoparticles they become more -ve for NaB~

molecules and more +ve for dye molecule. The electron transfer takes place from

reducing agent to dye molecule via metal nanoparticles, and result in the destruction of

the dye chromophore structure to form small species such as acetamide, S04-2, C02, H20.

6.4 CONCLUSION

This study demonstrates the reductive degradation of azo dyes usmg Ag

nanoparticles as catalyst in aqueous solution. The rapid degradation of the dye solution

was monitored spectrophotometrically and was found to fit the first order kinetic model.

The degradation was more efficient at higher pH (> 7.0). With increasing acidity of dye

solution the degradation rate decreased. FT-IR, MS and IC analysis of degradation

162


products revealed the reductive cleavage of the azo linkage to produced amines, amides,

S04-2

, C02 and H20, which are in very small amount and less hazardous than original

dye. Ag nanoparticle was successfully applied as catalyst along with surfactant SDS.

More significantly, Ag nanoparticles showed fast and rapid degradation with sustained

reactivity compared to other degradation technique like biodegradation, and making them

potential candidates for dye degradation technologies.

163


Figures and Tables

(a)

(b)

(d)

OH

(e)

OH

Fig. 1 Structure of (a) Red 5B; (b) Red 6BX; (c) Acid orange; (d) Orange 2R; (e) Patent Blue

164


Fig. 2 Transmission Electron Microscope image of silver nanoparticles

C) c 1 (':

Q, :::t 0

100

90

80 70 60

40 30

20

10

I I$$ fHI

.... .!..,...£. .. ' ... \:.;.~!. ...... .! .. .! .. \ ! f I ' ~ >.Ht ' ~ }

1 1 'J tnl * l

1 1 t • j ~ nt , ' ! ...... ,. ... i' -.J-,-~"';; !":i-- '-;: ... '";-: ' , ' ' ~ j ; •

..... !...,:0-' .. \12;..~!. ..... .;_~ ... •• I 1 l ~ I HU ; < ~

~ > ~ I I I ; I \.

..... -.~..,..-,.; ... tJ,J ~iL .. •"" ... ~-\ > l < > > >Ut l < '

l t ~ J 1 Ht

--~-·-~J~~~--~-~-~ l ~ > ! < I If

-·•-~-~J~~L- ... ~-~-~ J t 4) $ !IU

..... 4o,,.;.. -'•'..1J. io!L.•- .# .... ••'-) ' j s ) ~ ~ ,, ~ !

..................................... --· I I i<,HI

• l ~ t i < ••

0 +--r-;..;;;.mr-.y...;.-rf¥ 0.000 0.001 O.Q1

t i liit<l

... ,:.,.!,j.I,J.!:J ... 'I * 1 j tf<,ll

--~·f~-:~~h: --+-+ ! f ~ j j. "''

........ ~ ....... !. ... .! ..! ... •.:.!~eq >I l ~ 1 I ' > ~ -i I

>I ~ \ I ~ tH I l f ---1.' --·-.4..1-~~.J\,Jt --•-•..J-·.J IJ > ~ I > > n < f I t J t t

•I ~ ) I I H \ t

0.1 1 Size(Mierons)

10

Fig. 3 Dynamic light scattering histogram of silver nanoparticles

165


1.0

0.0

0.8

0.7

8 ij

0~

-e 0.0 0

~ 0.4

0.3

0.2

0.1

0~

300 ..., 000 000 700

Wavelength

Fig. 4 UV-vis absorbace spectra shows Plasmon peak (422 nm) of silver nanaoparticles

0.8

0.7

06 .. g 05 ..

-!:! 0.4 0

~ 0.3

02

0.1

0.6.,

05~

A 0.8 c

07 i Mi . ;

g 0.5 .· • ~ 0.4

~ 0.3 0:2.

B

0.1·~ .350 400 450 500 550 600 0 .L~~~~==::::~~.__......, __

Wavelenglll(nm)

c

400 SOD 600 Wavelenglll (nm)

0.4

~

no;·

~ 0.4~ t: ~

~ 0.3·1 ~ 02!

350 400 450 500 550 600 Wavelenglll (nm}

D

00~~~~~~~~~~~~--~~ 300 400 500 600

Wavelenglll (nm)

E

l"~ ~ 02

0.1

400 500 600 700

Wavelenglll (nm)

Figure 5. UV-visible spectral changes of (A) Red 58; (B) Red 6BX; (C) Acid orange; (D) Orange

2R; (E) Patent Blue dye (1.0 x 10-4M), the topmost to bottom show decreasing the concentration

of dye.

166

Chapter 6 Silver nanopartic/es

Table 1: The molar absorptivity of dyes at the 1.0 x 10-4 M concentration

Dye Amax (nm) € (mor em·)

R5B 510 5020

R6BX 508 6950

AO 484 4750

02R 480 4880

PB 658 3120

____ R6BX

Figure 6. Reappearance of original silver nanoparticles color after degradation of dye.

167

Chapter 6

0.00012

0.0001

l 0.00008 , .... 0 u 0.00006 c: 8 0.00004

0.00002

0

0 5 10

nme(min)

15

Silver nanoparticles

~RSB

-R6BX

~AO

_._02R

--11-PB

Figure 7. Dye concentration changes as a function of time (Concentration of dye: 0.0001 M)

168

Chapter 6

0.00012

CD 0.0001 X! 'S 0.00008 c 0

~-~ 0.00006

" 0.00004 c

s 0,00002

'S c 0

~ " c

s 0.00002

0 2 4 6

lime{mln)

8 10 12

oL~---·-···· 0 2 4

·---·-·----··

6

time{min)

0.00012

0.0001 lZI ... - 0.00008 0 c 0

l 0.00006

0.00004 c 0 u

0.00002

0

8 10 12

0 2 4 6

000012

>< 0.0001 lZI

~ 'S 0 00008 c 0 0.00006

1 " c s

< 0 'S c 0

~ l! c 0 u

000004

0.00002

0.00012

0.0001

0.00008

0.00006

0.00004

0.00002

0 2 4

0 ·--·--·---0 2 4

8 10 12 14

Silver nanoparticles

6

lime(min)

6 8

time(min)

8 10 12

10 12 14

Figure 8. Concentration profiles of (a) R58; (b) R6BX (c) 02R (d) OA and (e) PB when

degraded with the initial concentration of (•) 1.0 x 104 M (•) 0.5 x 104 M(.&) 1.0 x 10·5 M.

169


Table 2 slopes of dyes at different concentration (loge vs time )

Dye 1.0 X 1004 M 0.5 X 1004 M 1.0 X 10"5 M

R5B -6.544 -6.643 -6.643

R6BX -9.698 -9.698 -9.698

02R -6.092 -6.093 -6.092

AO -12.490 -12.490 -12.491

PB -8.569 -8.569 -8.568

60

50

..... 40 .

..J -+-R5B C)

E 30 __._R6BX Q 0 -a-AO () 20

-o2R 10 -&-PB

0

0 5 10 15

Time(min)

Figure 9. Variation in COD during the course of direct degradation of dye (1.0 X 104 M, 50 ml)

170


(a)

R5B

(b)

AO (b)

02R (b)

PB (b)

3XO 2fO) Z1Q) 1800

Wavelength (nm)

Figure 9. Variation of IR spectra in the degradation of dyes (a) before degradation and (b) after

degradation

171


11:10 st

Ill,) CHaCOt1H2

I ~

~-:t

fO

n :0

~ 10 ;., fO ;0

to

co "' CH(ttH2~

\to ~

CICH2ttH2 Jl I ~

ao •> ll •• .~

:0

avo , .. ... ········•··············· .................. , ...... .

w i"l eo " "*

Ill) AO >.

:!::

"' c .. 1:0

:1; • :> ao i 4i tl:;o

IOC> II>

02R Ill)

1:0

•• ao

:0

IOC> . ,.

~

PB 110 •>

110

ao

:0

0

·~

Figure 10. Mass spectra of mineralized component of degraded products (from GC-MS

spectroscopy)

172


9

8

7

6

5

"' 4 E

3

2

1

0

-1

lime(min)

Figure 11. Effect on sulphate ion peak before and after degradation of dye (1.0 x 104

M, 100 ml)

0.6

0.5 (I)

0.4 (,)

c: co -+-pH2 .Q 0.3 .. 0 -a-pH4 fn .Q 0.2 <( ...,..pH6

0.1 -*-PH7-10

0

0 10 20 30

Time (minute)

Figure 12. Variation of pH (2-10); 1.0 X 104 M R5B dye concentration.

173


Dye•

t Degraded dye

Surfactant layer

Destruction of Chromofore Structure

Final Products

Acetamide(R5B)

Methanetrlamlne {R6BX and 02R)

Dlethyl amine (PB)

Figure 13. Degradation Pathway of dye

174


References

[1] K. Vinodgopal, P. V. Kamat, Environ. Sci. Technol., 1995, 29, 841.

[2] G. Liu and J. Zhao, New J. Chern., 2000, 24, 411.

[3] S. Hammami, N. Oturan, N. Bellakhal, M. Dachraoui, M.A. Oturan, J. Electroanal. Chern., 2007, 610, 75.

[4] C. C. Cariasa, J. M. Novaisa, S. Martins-Dias, Biores. Technol., 2008, 99, 243.

[5] U. U. Jadhava, V. V. Dawkara, G. S. Ghodakea, S. P. Govindwar, J. Hazard. Mater., 2008, 158, 507.

[6] K. M.G. Machado, L. C. A. Compart, R.O. Morais, L. H. Rosa, M. H. Santos, Braz. J. Micro., 2006, 37,481.

[7] J.H Hodak, !.Martini, G.V Hartland, J. Phys. Chern. B, 1998, 102, 6958.

[8] P.V.Kamat, M. Flumiami, G.V. Hartland, J. Phys. Chern. B, 1998, 102,3123-3128.

[9] S.L. Logunov, T.S. Ahmadi, M.A. El. Sayd, J.T. Khoury, R.L.Whetten, J. Phys. Chern. B, 1997, 101, 3713.

[10] V.Rotello (Ed.) Nanoparticles Buildings Blocks for Nanotechnology, Kluwer Acd./ Plenum Publishers, New York, 2004.

[11] G.Schmid (Ed.) Nanoparticles from theory to application, Wiley-vch, 2004.

[12] A.Sharma, J.Bellare (Ed.) Advances in Nanoscience and Nanotechnology, National Inst. of Sci. Comm. and Information Resouces (CSIR), 2004.

[13] A.Henglein, D. Meisel, J. Phys. Chern. B, 1998, 102, 8364.

[14] A.Taleb, C. Patit, M.P. Pileni, J. Phys. Chern. B, 1998, 102, 2214.

[15] J.H Hodak, A Henglein, G.V. Hartland, Pure Appl. Chern., 2000, 72, 189.

[16] H.Fujiwara, S.Yangida, P.V. Kamat, J. Phys. Chern. B 1999, 103, 2589.

[17] J.Hodak, I. Martini, G.V. Hartland, Chern. Phys. Lett, 1998,284, 135.

[18] S.W.Han, Y.Kim, K.Kim, J. Collid. Interf. Sci., 1998,208,272.

[19] M.Haruta, Catalysis Today, 1997,36, 153.

175


[20] T. Hayashi, K. Tanaka, M. Haruta, J. Catal., 1998, 178, 566.

[21] N.Pradhan, A. Pal, T. Pal, Langmuir, 2001, 17, 1800.

[22] T. Pal, S. De, N.R Jana, N. Pradhan, R. Mandai, A. Pal, A.E Beezer, J.C Mitchell, Langmuir, 1998, 14, 4724.

[23] N.R. Jana, T. Pal, Langmuir, 1999, 15, 3458.

[24] B.V Enustun, J. -:(ur~evich, J. Am. Chern. Soc., 1963,85,3317.

[25] G.H Jefferi, J. Bassett, J. Mendham, R.C Denney, Vogel's Textbook of quantitative chemical analysis, John Wiley and Sons. Inc, Newyork, 1989.

[26] J.H Fendler, Chern. Rev., 1987, 87, 877.

[27] T.Pal, T.K Sau, N.R Jana, Langmuir, 1997, 13, 1481.

176

Documents

CHAPTER6 Silver nanoparticles as a catalyst for ...shodhganga.inflibnet.ac.in/bitstream/10603/35165/11/11_chapter6.pdf · Silver nanoparticles as a catalyst for degradation of hazardous